Insofar as such measurement transmitters are often applied under adverse environmental conditions, one attempts to prevent breaks in the housings of the measurement transmitters, since, through such breaks, corrosive or explosive media could penetrate into the housing of the measurement transmitter. Thus, interacting with the measurement transmitters via keys with galvanic contacts and switches is limited. In order nevertheless to enable interaction with measurement transmitters, for example, buttons with a magnetic element are used, which have defined positions relative to the measurement transmitter and are movable, in order with their magnetic fields to actuate corresponding magnetic switches or Hall sensors in the interior of the housing.
Thus, Offenlegungsschrift (laid open application) DE102004036324 A1 discloses a magnetic switch for a measurement transmitter, in the case of which a support body, which contains a magnetic element in asymmetric position, can be inserted in different orientations into a blind hole, which borders the inner space of a housing, wherein, depending on the orientation of the magnetic element in the blind hole, a Hall-sensor in the interior of the housing is influenced differently by the magnetic element. By selection of the orientation of the magnetic element, one of two manners of operation of the measurement transmitter can be selected.
European Patent EP0 383 823 B1 discloses a measurement transmitter, in the case of which zero-point and slope can be set by means of magnetic switches, wherein each of the magnetic switches has a magnet, which is movable in a blind hole, in order to actuate a reed-contact arranged in an electronics housing of the measurement transmitter and positioned in the vicinity of the wall of the blind hole.
With reference to platform concepts, it can, however, be quite advantageous to offer simple device variants without magnetic switches, when the interactive functions resulting from the magnetic switches are not required.
In this case, however, attention must be paid that not using the magnetic elements still leaves operation of the electronic device with a standardized electronic circuit possible, that, thus, a control- and evaluation circuit is suitable to function reliably in both variants of an electronic device. This means in particular that the circuit is able to detect the presence of a magnet and to distinguish from magnetic disturbance fields arising in given cases. It is, therefore, an object of the present invention to provide an electronic device and a method for its start-up, wherein the electronic device can be operated reliably both with magnet switches as well as also without magnetic switches.